Effect of silica gel pores size on the formation of γ-Fe2O3/Q nanocatalyst

The paper analyses the synthesis of iron oxide nanoparticles using SiO2·9H2O silica gels of different porosity as a reaction vessel. The influence of pore sizes of used SiO2·9H2O silica gels on the processes occurring at all stages of synthesis of nanocatalysts - iron oxide nanoparticles, conducted directly in the silica gel pores, has been investigated. All stages of synthesis were investigated by X-ray diffraction and Mössbauer spectroscopy. It is observed that a narrow size distribution of iron oxide nanoparticles occurs in the 10 nm size pores, while in the 30 nm pores the distribution is much wider. By nitrogen adsorption-desorption method, it was found that the pores themselves have a size distribution around the pore sizes stated by the silica gel manufacturer (Q-10 and Q-30 nm). The 10 nm pores have a narrow size distribution, while the 30 nm pores have a broad size distribution and complex internal structure. It is shown that the nanoparticle size distributions correlate with the pore size distributions. The size distribution of the obtained iron oxide nanoparticles is determined by the size distribution and curvature of the pores in which they were synthesised.